The present invention relates to a telescoping aerial refueling probe, and more particularly to a lightweight actuation system therefore.
Typically, telescoping aerial refueling probes are actuated pneumatically using engine bleed air. The hot bleed may dry out the probe""s seals and cause corrosion of the telescoping sections which creates a stiction problem during extension and retraction. In addition, a relatively large quantity of bleed air is required to operate the probe within an acceptable time period. Usage of bleed air reduces the power available to the propulsion system.
Other telescoping aerial refueling probes are actuated hydraulically using fuel as the pressure medium. A first tube extends telescopingly from a second tube. Chambers are formed between the first tube and second tube to receive fuel. To extend the probe, an extension chamber is pressurized with fuel. Likewise, to retract the probe, a retraction chamber is pressurized with fuel and the extension chamber is connected to drain. Disadvantageously, the fuel-driven probe is relatively heavy as additional fuel lines, valves and specific high pressure pumps. Also, a quantity of fuel may always remain within multiple chambers of the probe. Trapped fuel is unusable to the propulsion system, increases system weight, and disadvantageously affects ballistic tolerance.
Due to the complexity and weight of both the pneumatic and fuel-driven systems, it has been difficult and weight-prohibitive to incorporate redundant actuation systems. Lack of redundant systems reduces the level of confidence in completion of long-range missions which do not provide the option of landing to refuel.
Accordingly, it is desirable to provide a refueling probe that is reliable, lightweight, and ballistically tolerant. It is further desirable that the probe include a redundant actuation system.
The aerial refueling probe according to the present invention includes an outer section, an inner section and a ball screw. The inner section is telescopically mounted within the outer section. The ball screw is rotationally mounted along a longitudinal axis of the outer section. A ball screw nut is mounted to a vehicle end of the inner section. The inner section has at an end opposite the vehicle end a valve such as a MIL-N-25161C Flexible Tip Nozzle.
A hydraulic motor rotates the ball screw to drive the ball screw nut and therefore the inner section relative the outer section. The hydraulic motor communicates with an aircraft hydraulic system and is operated in response to a control system. The probe includes three modes of probe operation: RETRACT, EXTEND, and REFUEL to selectively operate the hydraulic motor; and to transfer fuel into the fuel tank in the refuel mode.
A backup motor such as an electric motor operates to drive the ball screw upon failure of the hydraulic motor. Operation is essentially transparent from an operator perspective. As only the backup motor is required for redundancy, minimal additional weight is added to the probe and a relatively compact system is provided.
In operation, the pilot initiates the probe by selecting EXTEND which disengages a locking device and actuates the hydraulic motor. The hydraulic motor operates as a turbine, in which fluid rotates the hydraulic motor to rotate the ball-screw. Rotation of the ball screw drives a ball screw nut secured to the inner section. Translation of the nut drives the inner section relative the outer section. When the inner section contacts a limit switch stop or the like, the hydraulic motor stops and a locking device actuates to secure the inner section in the extended position. The probe is ready for aerial refueling. The procedure is essentially reversed for probe retraction.
The present invention therefore provides a refueling probe that is reliable, lightweight, ballistically tolerant and incorporates a redundant actuation system.